The Imaging Core will provide essential support for the PET studies (Projects 1-3) and the MR studies (Project 2) proposed in this application. In these studies, multiple radiotracers will be administered intravenously to all research participants in conjunction with PET imaging. In Project 1, Parkinson's disease (PD) patients and healthy volunteer subjects will be scanned with [ [18] F]-FDG PET (to measure glucose metabolism), [[15] 0]-H20 PET (to visualize cerebral blood flow) and [ [82]Rb] PET (to assess blood brain barrier (BBB) permeability). In Project 2, PD patients will be scanned with [18] F-FDG (for glucose metabolism), [[11] C]-PIB (to detect protein aggregation), and [[18] F]-FPCIT (to trace striatal dopamine transporter binding). In Project 3, subjects will also undergo FPCIT PET imaging.